Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.78	6.457%	$182.8718	$182.87	$182.85	$182.90
Purchase #2	$48.55	5.777%	$51.3547	$51.35	$51.35	$51.40
Purchase #3	$38.92	5.195%	$40.9419	$40.94	$40.95	$40.90
Purchase #4	$92.75	13.695%	$105.4521	$105.45	$105.45	$105.50
Purchase #5	$42.29	9.740%	$46.409	$46.41	$46.40	$46.40
Purchase #6	$23.77	7.174%	$25.4753	$25.48	$25.50	$25.50
Purchase #7	$118.43	13.367%	$134.2605	$134.26	$134.25	$134.30
7 purchase totals =	$536.49		$586.7653	$586.76	$586.75	$586.90